1. Technical Field
This invention generally relates to a bearing and seal assembly for use with portable, powered, mortar mixers having a horizontally oriented mixing drum rotatable from a mixing position to a dumping position and a powered paddle shaft extending coaxially therethrough with radially extending paddles and power means for mixing mortar. More particularly it relates to a dual action bearing and seal assembly for supporting a rotatable paddle shaft and the rotatable drum which can be lubricated with grease through a grease fitting rigidly and permanently connected to a grease pump attached to the mortar mixer.
2. Background Art
Brick layers, and masons in general, need a means of mixing mortar at job sites where brick or stone work is to be accomplished. Traditionally mixing mortar has been a job assigned to the brick layer's assistant, sometimes called a hog carrier, and was done by hand. In recent years portable, power driven, mortar mixers have come into common usage.
It is useful to describe a typical mortar mixer in order to fully understand the import of the present invention.The typical portable mortar mixer is mounted to a utility trailer frame and is towed from job site to job site. It has a horizontally oriented cylindrical mixing drum which is open at the top and rotatable from an open top position into which mortar, sand and water are dumped for purposes of mixing, to a dumping position where mixed mortar is dumped onto a mortar board for use by the mason. A paddle shaft extends through and is axially aligned with the horizontal drum. Extending radially from the paddle shaft are a plurality of paddles which are used to mix the combination of materials into suitable mortar. Power is provided by a gasoline engine.
Since both the paddle shaft and the drum are independently rotatable, the bearing support system for the mortar mixer, as a general rule, has to include at least a pair of concentric rotatable shaft assemblies, one for the paddle wheel and the second for the drum. The environment in which these bearing assemblies are used, can at best, be described as hostile. They are used in all sorts of weather conditions and, are located in very close proximity to the abrasive mixtures of mortar, sand and dust. As a result maintaining proper lubrication for the paddle shaft and drum bearing assemblies is difficult.
TERTINEK, ET AL., U.S. Pat. No. 3,932,006 discloses a paddle shaft seal assembly which is typical of that in use today. As can be seen in Tertinek, the lubricant is grease, and it is injected into the paddle shaft bearing through one grease fitting, and into the drum bearing assembly by another grease fitting. The reason why two separate grease fittings are used is the fact that the independent rotation of the two concentric shafts, by definition results in one shaft housing rotating relative to the other.
The problem is that the bearing assembly such as that disclosed in Tertinek, must be greased periodically, and since there are two independent grease fittings, at least one of which must rotate relative to the other and/or the mortar mixer frame, lubrication can only be accomplished by use of a hand-held grease gun and independent grease fittings for each bearing assembly.
Another problem arises by reason of the close proximity interface between the motor drum containing a white or light colored mortar, and a heavily greased bearing assembly. The greased bearing assembly must be protected from infiltration of abrasive mortar and dust, and at the same time grease must be kept out of the mixing drum and away from the mixed mortar where it will cause discoloration. The traditional solution to both of these problems is to seal the junction between the paddle shaft and the bearing housing with grease packed rubber sealing rings interspaced between various configurations of metal spacers and held in place by an overpressure of packed grease. Again see Tertinek, et al. for a typical configuration.
This is not a satisfactory solution for two reasons. The first is that the packed grease slowly, but steadily, escapes from the bearing assembly, and oftentimes travels along the paddle shaft into the mixing drum where it contaminates mortar mix. This occurs most often with a bearing assembly that is properly packed with grease but has worn seals.
A second, and more common problem, is that oftentimes the bearing is not properly packed. The reason is that it requires a portable grease gun for use in injecting grease. The portable grease gun must be carried to remote locations with the machine, and it is often forgotten, mislaid, or pilfered, with the common result that the bearing assemblies go ungreased for long periods of time.
A solution would be to provide some sort of an automatic or hard plumbed grease gun system made integral with the mortar mixer unit whereby grease could be periodically injected into the bearings to keep them properly packed. A hard plumbed system such as this, being integral with the utility trailer, would always be available and not subject to being forgotten, mislaid, or pilfered. The problem is that at least one of the two bearing housings, either for the drum, or the paddle shaft, will rotate relative to the other. Until now this has made the installation of a hard plumbed greasing system, impossible.
Accordingly it is an object of this invention to provide a dual bearing and seal assembly for use with a mortar mixer, in which both the paddle shaft bearings, drum bearings and grease seals can all be greased through the use of one grease fitting that is stationary with respect to the mortar mixer frame.
A second object of the present invention is to provide a shaft sealing system that prevents the discharge of grease from the bearing assembly yet at the same time prevents the infiltration of abrasive mortar mix or dust.